1. Melt the butter in a medium saucepan over medium-high heat.
2. Add the onion, and cook, stirring, for 3 minutes.
3. Add the flour and cook until golden, 1 to 2 minutes more.
4. Stir in the cheese and stock, and simmer until thickened, 5 to 10 minutes.
5. Stir in the broccoli and cook until heated through.
6. Season with salt, pepper, and paprika, if desired.